A technology for driving switching elements (semiconductor elements) used in power converters or the like includes a technology of forming a gate drive circuit with a simple configuration composed of a small number of components by actively using the gate capacitance of the semiconductor element (for example, see Patent Literature 1 described below). With this technology, the gate drive circuit, in which a capacitor and a resistor are connected in parallel, is inserted between the gate and the switching output circuit such that the relationship between the gate capacitance Cis of the semiconductor element and the capacitance Cg satisfies (switching-control-circuit output voltage at the time of turn-on)×(Cg/(Cg+Cis))≧(threshold voltage), and the resistor of the gate drive circuit supplies to the gate of the gate-drive-type semiconductor element with a current appropriate for the conductivity modulation. Accordingly, the output voltage of the switching control circuit is appropriately divided and applied to the gate terminal of the semiconductor element, thereby realizing a gate drive circuit with a simple circuit configuration composed of a small number of components.
Moreover, there is a technology for reducing the reverse recovery current of a freewheeling diode by using a circuit that applies a voltage lower than the applied voltage in a steady state for a certain period of time set by a timer at the time of turn-on or by using switching elements having different switching times as a pair of switching elements in the output stage of the gate drive circuit and by setting a voltage to be applied to the gate of the semiconductor element relatively low (for example, see Patent Literature 2 described below).
Moreover, there is a technology in which the gate voltage gradually increases at the time of turn-on due to the capacitor connected between the gate and emitter; however, at the time of turn-off, the capacitor does not function and thus dv/dt does not become gradual, thereby preventing the switching loss from being increased (for example, see Patent Literature 3 described below).